1. Field of the Disclosure
The present disclosure relates generally to a media retractor and recycler system for use with automatic document feeders and duplexers, and, in particular, to a media retractor and recycler that concurrently supports two media sheets for duplex printing or scanning.
2. Description of the Related Art
A typical media feed system for automatic document feeders to allow scanning of both sides of a document employed in an all-in-one device (AIO)/multifunctional device, has a pick unit (assembly) for picking media sheets and one or more pairs of feed rolls to drive the media sheets through a feed path/loop extending to and from a scanning module of the AIO device. The pick unit and each pair of rolls from the one or more pairs of rolls around the loop are generally operated by a driving mechanism, such as a motor. The media feed system may further include a clutch mechanism adapted to engage/disengage the driving mechanism with the pick unit. Specifically, the clutch mechanism may disable picking of a media sheet by the pick unit when a previous media sheet is still in the feed path. The media feed system also includes a pair of exit rolls that may operate with the help of either the same clutch mechanism or a different clutch mechanism adapted for running/rotating each exit roll of the pair of exit rolls either in a clockwise direction or in an anti-clockwise direction. Specifically, each exit roll of the pair of exit rolls may be rotated either to drive a media sheet into an output stack or to retract the media sheet back into the feed path for duplex scanning. A similar media retractor and recycler system may be employed with a duplexing printer wherein each side of the media to be printed is directed past a print engine, such as an electrophotographic print engine or an inkjet print engine.
Typically, a media sheet is required to make three passes through a feed path in order to facilitate scanning of both sides (duplex scanning) of the media sheet and stacking of the media sheet in a collated order. The media sheet nearly completes the three passes before a next media sheet is picked-up, as the length of the media feed path is designed to hold only one media sheet at a designed for length. For instance if A4 (210 mm×297 mm) and 8½×11 inch media types are to be scanned the length of the feed path would be at least 297 mm to accommodate the longer of the two media types. FIG. 1 illustrates a typical media feed path for a duplex scanner designed to hold a single media sheet at a time for image processing.
FIG. 1 shows a media path of an imaging device 100, such as automatic document feeder (ADF) and an image processor B, such as scanner 192 for an AIO device (imaging device). As shown in FIG. 1, imaging device 100 includes a pick assembly 110 having a pick roll 112; a drive roll 119, two feed roll assemblies 120, 130 to drive a media sheet 114 positioned in input area 116 around a first media path 140 (feed path); a diverter structure, such as gate 150; and an exit roll assembly 160 that rotates bi-directionally or is reversible. Roll assemblies 120, 130, and 160 each includes a pair of rolls forming a nip therebetween. One roll or both rolls in each roll assembly may be driven. The pair of rolls in each of feed roll assemblies 120, 130 and exit roll assembly 160 form respective nips 120N, 130N, and 160N. Exit roll assembly 160 may be driven in an exit direction E and it may be reversibly driven in a retraction direction R and may employ a mechanism as is known in the art to vary the height of nip 160N as one means of varying nip pressure. As is known through use of linkages and transmissions, a motor 170 drives or rotates drive roll 119 and feed roll assemblies 120, 130 to enable media sheet feeding along first media path 140. Similarly, a second motor 172 and clutch 182 are shown for driving pick assembly 110 and pick roll 112 for picking a media sheet and feeding it into first media path 140. A third motor 173 is shown for driving exit roll assembly 160. While three motors 170, 172, 173 are illustrated, it will be recognized that a single motor may be used in place of motors 172 and 173 along with use of clutch 182 or use of an optional clutch 184 shown in dashed lines or use of both clutches 182, 184.
Media 114 exiting exit nip 160N is retained in output area 118. For duplexing, a second media path 142 (return path) is provided beginning at an intersection 144 with first media path 140 near exit roll assembly 160 and ending adjacent the start of media path 140 at an intersection 146 with first media path 140. The diverter structure, gate 150, is positioned at intersection 144 and is used to divert a media sheet being retracted by exit roll assembly 160 into second media path 142. First media path 140 begins adjacent pick roll 112 and extends to exit assembly 160, passing through feed roll assemblies 120, 130 and processing zone A and continues to intersection 144. First and second media paths 140 and 142 may be viewed as overlapping in the region between the diverter structure, gate 150 and exit roll assembly 160. Alternatively second media path 142 may be viewed as starting at intersection 144. Controller 190 is illustrated as being communicatively coupled to motors 170, 172, 173, gate 150, and various media position sensors, such as sensors S1-S3, which coupling is not shown for clarity, to control movement of media 114 along first media path 140 from input area 116 through output area 118 and along media return path 142. Sensors S1-S3 typically sense the leading and trailing edges of each media sheet as it travels along first and second media paths 140, 142. Diverter structure such as gate 150 and reversible exit roll assembly 160 comprise a media retractor and recycler assembly 200.
During a typical duplex scan, motor 170 rotates the drive roll 119, feed roll assemblies 120, 130 and exit roll assembly 160. Subsequently, motor 172 engages clutch 182 which engages pick assembly 110 causing pick roll 112 to pick a first media sheet 114-1 and driving it into first media path 140 to drive roll 119 from media stack 114 until first media sheet 114-1 reaches and is engaged by a first feed roll assembly, namely feed roll assembly 120. Either motor 172 is stopped or clutch 182 disengages from pick assembly 110 to prevent picking a subsequent media sheet. Drive roll 119 allows short media such as A6 media to be driven through the system. Should sensor S1 not detect the leading or trailing edge of first media sheet 114-1 and any subsequent media sheet, a fault may be declared by controller 190.
First media sheet 114-1 is then driven by feed roll assembly 120 to pass through a media processing zone A, where first media sheet may be printed or may be scanned by imaging processor B. As shown, a first side of first media sheet 114-1 is being scanned in media processing zone A by scanner 192. First media sheet 114-1 is then driven into nip 130N of feed roll assembly 130 which in turn drives it past a diverter structure, such as gate 150 that is positioned by controller 190 as shown to direct first media sheet 114-1 into nip 160N of exit roll assembly 160 where it continues to be driven in exit direction E. Once a trailing edge of first media sheet 114-1 passes diverter gate 150 as sensed by sensor S2, motor 173 stops and reverses which in turn reverses exit roll assembly 160 rotation and feeds first media sheet 114-1 in retraction direction R. Again should sensor S2 or S3 not detect the leading and trailing edge of first media sheet 114-1 and any subsequent media sheet a fault may be declared by controller 190.
Subsequently, exit roll assembly 160 retracts first media sheet 114-1 into second media path 142 (return path) that, as illustrated, forms a loop with first media path 140. Specifically, as shown controller 190 positions gate 150 so that as first media sheet 114-1 is retracted it is directed into second media path 142. Alternatively gate 150 may be passive and operated by gravity to fall across first media path 140 after a trailing edge of first media sheet 114-1 passes allowing first media sheet 114-1 to be directed into second media path 142 when retracted. Once the leading edge of first media sheet 114-1 enters 120N again, motor 172 stops, and first clutch, clutch 184, disengages allowing exit roll assembly 160 to feed media again in exit direction E. Nip 160N may be allowed to open to reduce friction on first media sheet 114-1 that is applied by exit roll assembly 160 before motor 173 stops. Subsequently, first media sheet 114-1 is driven through nip 120N and into processing zone A and a second side of first media sheet 114-1 is then scanned in media processing zone A by an image processor B, such as illustrated scanner 192. As first media sheet 114-1 is being scanned its leading edge is driven into nip 130N before its trailing edge exits nip 120N. Feed roll assembly 130 then continues driving media sheet 114-1 through processing zone A and past gate 150 which has been repositioned to its initial state and into exit roll assembly 160. If gate 150 is a gravity actuated gate, feed roll assembly 130 has sufficient force to push first media sheet 114-1 beneath gate 150 and into nip 160N. Once the trailing edge of first media sheet 114-1 passes gate 150 again motor 173 stops and changes rotation direction of exit roll assembly 160 from exit direction E to the retraction direction R. Nip 160N may be allowed to close, if open, when the trailing edge of first media sheet 114-1 as sensed by sensor S3 is between the processing zone A and feed roll assembly 130. Should only two motors be in use with motor 173 being used to control both pick mechanism 110 and exit roll assembly 160, then a clutch such as clutch 182 is used to ensure pick mechanism 110 will rotate only in a direction to feed media into first media path 140 while allowing exit roll assembly 160 to be able to rotate in both the retraction direction R or exit direction E as needed.
Exit roll assembly 160 stops when the trailing edge of first media sheet 114-1 passes by gate 150 as may be sensed using sensor S2. Motor 173 reverses, reversing exit roll assembly 160 which feeds first media sheet 114-1 fed back into second media path 142 and the first media path 140 for another time (third time). Thereafter motor 172 drives pick assembly 110 through clutch 182 to pick a subsequent media sheet after the trailing edge of first media sheet 114-1 approaches intersection 146 during the third time. First media sheet 114-1 then exits exit roll assembly 160 and is placed in output location 118, with the first side in a face-down orientation for proper collation. In this typical layout, motor 170 runs continuously, and the first and second clutches 184, 182 are disengaged from drive roll 160D of exit roll assembly 160 and pick assembly 110, respectively, while media sheets are being scanned, in order to achieve consistent media velocity during a scanning operation.
For media processing, exemplified by ADF 100, the drive and idler rolls 160D, 160N are typically designed to have a low nip force in order to allow the feed roll assembly 130 to overcome the nip force at drive and idler rolls 160D, 160N and provide a smooth motion of the media sheets at the image processing zone A, even when exit roll assembly 160 is driving a media sheets towards the output location 118. Alternatively, the height of nip 160N may be increased to avoid any interference during an image processing operation such as scanning or printing of the media sheets.
As depicted in FIG. 2, a length L1 of the gate-to-gate loop formed by following second media path 142 from gate 150 through first media path and back to gate 150 is about 11.8 inches (30 cm), i.e., approximately 12 inches (30.5 cm). Accordingly, it may be possible for a longer media sheet, such as legal (35.6 cm), to have a leading edge and a trailing edge thereof in the nip 160N at the same time. Hence the need to be able to increase the height of nip 160N. Further, a distance D1 from pick roll 112 to the feed roll assembly 120 determines the shortest length of media that can be scanned, i.e., media sheets shorter than length D1 may not be scanned in a simplex scanning mode, as a subsequent media sheet may be picked before pick assembly 110 is allowed to stop. As illustrated distance D1 is about 11.7 cm which allows A6 media sheet to be fed by first providing a short edge of the media sheet. Depending on the design of the pick assembly 110, a distance D2 from the drive roll 119 to feed roll assembly 120 may be about 7.9 cm which may determine the length of media that may be used in the processing zone A, for example, for a simplex scanning or printing mode. Further, a distance D3 from exit roll assembly 160 past gate 150 to feed roll assembly 120, which as illustrated is about 14.2 cm, is a dimension that is used to determine timing in a duplex scanning or printing mode, as distance D3 determines the minimum length of a media sheet that may be handled in such modes. Furthermore, overall horizontal dimension and vertical dimension of the loop may be about 11.2 cm by 6.6 cm, respectively (exclusive of dimensions of pickup roll 112, drive roll 119; feed roll assemblies 120, 130 and exit roll assembly 160). The above-mentioned distances between the roll assemblies of the 100 may be measured from respective nips thereof.
It has been observed that a scanning mechanism of an AIO device (such as the AIO device operatively coupled with the ADF 100) is typically designed to keep up pace with speed of a base engine (i.e., base printer engine of the AIO device). However, during a simplex scanning mode, speed of media sheets in feed path of ADF (such as the ADF 100) coupled to the AIO device, is faster than that of the base printer engine with longer inter-page gaps. Further, overall duplex throughput of the base printer engine (measured in terms of sides per minute (SPM)) is typically of the order of ⅕ of the simplex throughput for the ADF, whereas, the base printer engine is often much more efficient in the duplex scanning mode with a throughput ranging from about ½ to 9/10 of the throughput during a simplex scanning mode. Such a difference in the throughputs between the ADF and the base engine causes problems in addition to the loss of throughput. Specifically, the base engine may often need to transit between a ‘start’ mode and a ‘stop’ mode while waiting for subsequent scanned images that need to be processed, thereby resulting in mismatch in timing of the operation of the base printer and the operation of the scanning mechanism. Such a time-mismatch may cause additional wear and acoustic noises and may lead to thermal problems.
An existing solution to the aforementioned problems is to use a single pass ADF that includes a second scan bar fixed within a feed path loop of the ADF, thereby allowing capturing of both sides of a media sheet in a single pass. However, employing a second scan bar increases cost. Further, such an ADF allows for generating images at a speed much faster than the processing speed of a base printer engine associated with the ADF. Accordingly, a scanner mechanism of such an ADF is often required to transit between a ‘start’ mode and a ‘stop’ mode as the base printer engine processes scanned images at a slower pace.
Accordingly, there is a need for an efficient and a cost-effective media retractor and recycler that facilitates in achieving a sufficiently high throughput during a duplex scanning or a duplex printing and facilitates in reducing inter-page gap between consecutive media sheets.